When you perform an offline registration (via the Website), you are requested to generate a seed file. What is that file? A seed file is a file that incorporates elements from the machine, your license and the application you are running. It will be used to generate the license file that will be tied to the machine. A seed file is a text file whereas the final registration files are HTML files.
Note: the online activation (from within the 4D product) does not require seed files.